Investigating the cause of a damp patch on an internal wall, I discovered a
crack in a cast-iron downpipe; looking at it more closely I found that the
crack actually runs the entire circumference of the pipe, and it's possible
to raise the upper section and see daylight between it andthe lower
I know it would be a relatively trivial matter to replace the downpipe with
a 'nice new' plastic item; however, I'm rather attached to my original 100-
year-old cast-iron rainwater goods, and I'd really prefer to hang on to it
and repair it instead.
What would be the panel's reccommended method?
I'd be tempted to fashion a sleeve - possibly from a bit of plastic pipe
of similar diameter or slightly larger diameter. Cut the plastic pipe in
half - into two 'shells' - that can be offered up to each side of the
cast iron pipe. To get a good fit, a hot air gun can be used to soften
and slightly re-shape the plastic pipe.
The actual gap in between the two halves of the pipe could be bridged by
self-amalgamating tape (although this might not be necessary)
Butter-up the inner sides of the two halves of the shells with car body
filler (preferably the plastic type of Plastic Padding), and place on
each side of the cast iron pipe to form the sleeve. Hold in place with
wire or very large cable ties - or something much more businesslike -
like say several large Jubilee clips ('in series', as required).
I'd go for an *internal* sleeve; standard downpipe is probably too
large, but cut a suitable width axial slit so that it springs inside.
Fix with non-setting mastic, this can also be trowelled into the
external crack. Obviously, you would need to take down at least part of
the downpipe to do this.
As all you really need to do is stop it from leaking, I would lift the
upper part, clean the faces as best you can, apply gutter mastic and
join the two parts again. If it makes you feel more secure, put a bit of
flashband around the back half, covering the join.
If you want the "complete" repair, then clean off the paint, grind the
edge down so that the join is vee groove, preheat both bits to a couple
of hundred degrees, then braise in a joint. Once cooled off, grind flat
for an easier repair, cut the pipe with an angle grinder and stick in a
coupler. Cover that with a cast effect pipe shroud. e.g:
I buy mine, in the exact size needed*, from my local branch of these people:
They do a very quick delivery and are cheaper than buying the same clips
from the local agricultural supplier. If you do go down this route,
which I think will look awful, remember to specify stainless steel
* Sizes here:
They would be perfect. I'd use four of them - one at the top and bottom
of the sleeve, and one about an inch either side if the break.
But just a thought......
There's been a gas leak (on three occasions) in the cast iron mains pipe
buried deep in the verge outside my house. The pipe was about 4"
diameter, and they used a purpose-made sleeve to fix it. Presumably the
gas repairers have a stock of standard sleeves of various diameters, so
it might be useful to contact them to see if they can supply one. Of
course, such sleeves may be a standard part elsewhere in the
And a further thought....
Instead of car body filler, why not consider something rubbery - maybe a
piece of smooth rubber matting about 3mm thick.
if the pipe is painted though you would need to get rid of that. Most cast
iron is not that smooth, so you would need some kind of non shrinking filler
A word of warning though. Are you absolutely sure there are no other cracks
in the pipe? It tends to happen to cast iron if under any stress for a long
time that cracks grow and propagate, depending on where the minute flaws
are. It might be that in the end a new plastic pipe is less of a hassle.
From the Sofa of Brian Gaff Reply address is active
"Ian Jackson" < email@example.com> wrote in message
Certainly a better option, but he did ask for a repair and IMO, this is
the simplest way to meet the need to stop the leak. BTW it should be
possible to get an identical looking replacement in cast aluminium,
which is easier to handle and is less brittle.
Seems a lot of trouble for an unattractive result. I would have thought a
bit of flashing tape like this would be adequate.
Thanks all for the replies - some really useful info there. I think I
may use a hybrid of several responses! I've stopped it leaking for now
with h/d polythene sheeting and wire, so hopefully this job can now wait
till nicer weather next year.
Am particularly interested in the plastic 'lookalike' cast-iron stuff
above (or the Al range mentioned elsewhere) - I've never come across
that before. I have an immediate application for it. Several years ago
we had a block-paved drive done; there was a rather odd but quirky short
length of original downpipe which traversed a wall at 45 degrees to a
gully in the drive, but was admittedly in need of some maintenance. I
came home to find that the paving guy had removed and destroyed it, and
fitted a replacment modern placky component - a perfectly competent job,
and as he proudly said, at no extra cost - he took great pride in his
work and liked to leave a neat and tidy job and a happy customer.
"Thanks very much" I said, while inside screaming "AARGH - NOOOO!"
replying to Lobster, Celebration wrote:
So Lobster, interested in how this story ended: what did you did and are you
happy with the result?
I'm in a similar position, two front drainpipes in need of TLC but the local
tradesmen just want to rip them all out and replace with plastic (although I
know cast-iron effect is an option, it feels like an act of cultural vandalism
on an 1880s house!) I need to act swiftly as scaffolding is due to come down at
the end of the week!
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